Technical Abstract:
We have initiated genomic and proteomic studies to fully characterize the immunoproteome of the lepidopteran pest the budworm, Heliothis virescens. Larval budworm gene expression responses to bacterial and baculoviral infection were surveyed using expressed sequence tags (ESTs) generated from an immune-challenged hemocyte cDNA library. To date a total of 1496 ESTs have been generated and mapped onto structural, mitochondrial, and metabolic enzyme homologs of other insect species. Hemocytic transcripts of known or putative immune function were identified, e.g., zymogen prophenoloxidases (PPOs), enzymes of the PPO activating pathway, and C-type lectins. From the ESTs and 5’RACE sequences two hemocyte PPO subunits were assembled, HvPPO-1 and HvPPO-2. Expression of both subunits was constitutive, being unaffected by bacterial or baculoviral infection up to 72 hrs post infection. Expression of a C-type lectin was similarly unaffected. Digital gel electrophoresis (DIGE) of plasma proteins induced by infection followed by MS/MS of tryptic peptides revealed upregulation of many of the same proteins identified among ESTs, i.e. PPO and components of the PPO activating pathway. These complementary proteomic and genomic approaches indicate that bacterial or baculoviral infection upregulate PPO and its activation pathway post-translationally.